Lee Steele struck in the fifth minute of injury time of an astonishing game to seal Leyton Orient's promotion to League One and send his old club Oxford United down to the Conference after 44 years in the Football League.
Steele was one of four Orient players bearing down on goal and, despite looking offside, he turned in Gary Alexander's low cross from the left to send the 4,600 Orient fans wild.
The Oxford players gave it everything in front of a record Kassam Stadium attendance of 12,243, but had it not been for a series of stunning saves from keeper Billy Turley they might have been buried long before.
Turley was a controversial choice by Oxford boss Jim Smith, with most U's fans preferring Chris Tardif, but the recalled keeper made two vital saves in the first five minutes.
First, when Orient broke down the right Craig Easton hit a firece shot, but Turley blocked superbly. Then John Dempster allowed Lee Steele too much space, and the former Oxford striker's drive was flying into the net until Turley, at full stretch, finger-tipped it on to the post with Lee Mansell then completing the clearance.
Turley made a third save after 10 minutes from Wayne Cordon, who latched on to a mistake in midfield by Andy Burgess.
It was very much against the run of play when Oxford took the lead in the 14th minute. Eric Sabin was brought down and from Burgess's free-kick, Sabin got ahead of his marker and prodded the ball past keeper Glyn Garner.
It took only three minutes for Orient to equalise, Easton heading in a cross at the far post. Turley blocked the effort but the ball squirmed from his grasp and crossed the line.
Turley had to save again at a corner, but a rare opportunity came Oxford's way when Sabin won a tackle and burst through on the right side of the area only to blaze over.
In the second half it continued to be a very open, enthralling and tense encounter.
Orient looked to have booked their place in League One when Alexander put them in front after 63 minutes, chipping coolly over the keeper from Steele's pass after Matt Robinson had played him in.
Incredibly, though, Oxford clawed themselves back level two minutes later. Burgess's free-kick was met by Hargreaves, but although Glyn Garner parried his header, Chris Willmott powered home a follow-up header to make it 2-2.
The final few minutes were incredibly tense as supporters of both sides went through a rollercoaster of emotions.
But Steele had the last laugh against his former club, leaving Oxford, who won the Milk Cup 20 years ago, contemplating life in the Conference next season.